This invention relates to a machine for cleaning the surfaces of articles, such as metal castings and the like, by throwing abrasive at the surfaces of the articles as they are tumbled about in a cabinet. It relates more particularly to a means for conveying the articles into and out of the cabinet and for providing for a continuous tumbling action within the machine during operation.
The invention is related to a centrifugal blasting machine of the type described in the Peik U.S. Pat. No. 2,104,055. Briefly described, such machines comprise a housing completely enclosing a conveying means formed of a plurality of flights which extend crosswise between endless chains for travel about a predetermined path with the flights preferably in overlapping relation at their edges to form an endless, horizontally disposed belt on which the work or articles to be cleaned are supported. The flights of the belt travel between a driving sprocket and a guide roller spaced forwardly and below the sprocket. Between the rollers and sprockets there is usually provided a pair of spaced circular drums mounted for rotational movement about a horizontal axis between the sprockets and rollers with a peripheral portion of the drum extending rearwardly and below the sprocket and rearwardly and below the roller whereby the upper flight of the belt travels horizontally and in a downward direction beyond the roller and upwardly and in a forwardly direction in advance of the sprocket. As a result, when the belt travels in the direction from the roller to the sprocket, the work will be carried up the belt and be caused to tumble forwardly continuously onto the underlying work. The endless belt doubles back beneath the upper flight for travel about the forward roller and about a rearward roller to the sprocket.
The area between the drums is substantially completely enclosed by the belt and other portions of the housing including a doorway through which access may be had to the top flight of the conveyor belt for loading and unloading the machine. One or more centrifugal blast wheels for throwing abrasive particles into the housing and onto the work are mounted on the housing with suitable attachments for feeding and driving the units. A detailed description thereof will not be made since they form no part of this invention and are adequately described in the aforementioned issued patent.
An improvement upon the Peik patent is described in a patent issued to Kenneth H. Barnes, U.S. Pat. No. 2,909,012. In this patent there is described a tumbling mill or centifugal blasting machine which maintains the flight bars of the conveyor substantially in continuous contacting relationship one with the other to provide a continuous conveyor which is free of openings between the flights during travel.
A refinement of the Barnes device is disclosed in U.S. Pat. No. 3,079,735 to Freeman which provides a continuous conveyor which is free of openings between the flights by virtue of a flexible sealing element provided for that purpose.
In the Freeman and similar prior art devices the flights are formed of relatively expensive materials, such as manganese, which are selected for their resistance to blast treatment. Such materials, of course, are relatively expensive and it is desirable, therefore, to minimize the use of such material to the extent practical. In that regard the Freeman device employs a system for joining the link and flight in which mounting holes are provided in the blast resistant portion of the flight. A connecting mechanism, in the form of a reinforcing bar attached to the link, is then secured to the flight bar by means of bolts which are received in the mounting holes in the blast resistant portion. In order to obtain maximum life from the flight, it is necessary that the bolts used also be of blast resistant material. Forming counter sunk holes in the blast resistant portion of the flight and providing blast resistant bolts significantly increases the cost of the flights.
It is accordingly an object of the present invention to provide a link and flight assembly in which the use of manganese or similar blast resistant material is minimized.
It is a further object of the invention to secure flights to links in a low cost manner not requiring the use of expensive, blast resistant fastening devices.
A further object of the invention is to provide a link and flight assembly in which the elements are interconnected without the need for tapping or drilling the surface of the flight which is subject to blast treatment thereby strengthening the assembly. The invention also provides for use of a backer bar extending full length of the flight. This provides maximum back-up strength for the flight.
Another object of the invention is to provide a novel linking arrangement for a link and flight assembly.
Other objects and advantages of the invention will be apparent from the remaining portion of the specification.